estion 5 of 14 Sapling Learning A weightlifter bench-presses a 17o.0 kg barbell

Question

estion 5 of 14 Sapling Learning A weightlifter bench-presses a 17o.0 kg barbell from his chest to a height equal the length of his arms 0.850 m. How much work does he do? Number What is the potential energy of the barbell relative to the weightlifters chest after he lifts the barbell? Number How many food calories does the weightlifter use if he does this lift 35 times? Assume the weightlifter does no work in letting the barbell drop back to his chest. Number Cal o Previous Give Up & view Solution Check Answer ONext sl Exit Hint

Explanation / Answer

a)Work = Force * distance

The force is applied on the barbell against the gravity..
Force = Weight of the barbell...
Force = 170* 9.8 = 1666 N

Work = 1666 * 0.850 = 1416.1 J

b)

Potential Energy = mgh ( h is relative to the weight lifter's chest... so h = 0.850)
= 170 * 9.8 * 0.850 = 1416.1 J

c) He lifts it 35 times..
So total energy = 1416.1 * 35 = 49563.5 J

1 food calorie = 4185 J
1 / 4185 food calorie = 1J
49563.5 J = 49563.5 /4185 food calories

= 11.84 food calories

Related Questions

Navigate

• Browse (All)
• Browse E
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.